Method for the conversion of cellulose and related carbohydrate materials to low-molecular-weight compounds

ABSTRACT

Methods of converting cellulose or related biorenewable carbohydrate materials into high-value chemical compounds. The methods provide a means of converting low-cost materials such as cellulose and biomass into high yields of compounds such as ethylene glycol, propylene glycol, glycerin, methanol, hydroxyacetone, glycolaldehyde and dihydroxyacetone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/962,770, filed Dec. 8, 2010, which further claims priorityunder 35 U.S.C. §119 to U.S. Provisional Application No. 61/267,619,filed Dec. 8, 2009, each of which are herein incorporated by referencein their entirety.

FIELD OF THE INVENTION

The invention relates to methods of converting cellulose and relatedcarbohydrate materials to low-molecular-weight compounds, includingethylene glycol, propylene glycol, glycerin, methanol andhydroxyacetone. The invention provides methods for a single stepconversion of biomass sources to low-molecular-weight compounds througheither batch, campaign-type or continuous processes that do notnecessitate hydrogen gas, strong acids, metal catalysts, or enzymes. Theinvention further provides methods employing various co-solvents for theconversion of the biomass sources to low-molecular-weight compounds.

BACKGROUND OF THE INVENTION

Biomass is an abundant and renewable resource. As a result of suchavailability of biomass there is a significant need for improved methodsof biomass conversion. There is a vast body of work of others skilled inthe art attempting to convert biomass sources into desired, high-valuecompounds. See for example, U.S. Pat. No. 7,494,637. However, biomassconversion methods have consistently failed to yield high volumes and/orprovide efficient methods to convert biomass sources into high-valuecompounds as has been achieved by the present invention. For example,current industrial production of compounds such as propylene glycol andethylene glycol require the use of petroleum and do not convertrenewable sources. In such methods, ethylene or propylene are epoxidizedfrom alkenes to form oxides which are hydrolyzed to form the ethylene orpropylene glycol. As a result, such methods require significant andundesirable dependence on petroleum for the products of these biomassconversion processes.

Methods to efficiently convert biomass sources into these same desiredcompounds, including propylene glycol and ethylene glycol, wouldminimize the necessity of petroleum products for the production ofcommercially useful low-molecular-weight compounds and chemicals.Biomass conversion would further limit the large amounts of cellulosicwaste, or biomass, which if not utilized is generally left to decay,either in a landfill or in open fields. Therefore, there is significantdemand for the use of renewable starting materials, such as biomass, toproduce valuable products as described in the present invention.

Presently, very little biomass is converted into commercially-usefulcompounds. This is largely due to the fact that conversion of biomass,such as agricultural waste products, is difficult due to the complexstructure of plant cell walls. The plant cell wall is made oflignocellulose, which consists approximately of cellulose (38-50%),hemicellulose (17-32%) and lignin (15-30%). These components aredifficult to break down as the cellulose is made up of crystallinebundles of polysaccharide chains of β-1,4 bonded glucose molecules.Additionally, the hemicellulose consists of chains of amorphouscombinations of the sugar molecules xylose, mannose and arabinose. Thefinal component of lignocellulose is lignin, a macromolecule ofsubstituted phenols acting to bind together the lignocellulose matrixwhich provides strength to cell walls.

Various methods for converting lignocellulose require the use ofcatalysts, enzymes, or other expensive ingredients to depolymerizeand/or decrystallize the complex structure of the lignocellulose ofbiomass precluding the development of an efficient and effectiveone-step conversion process. See M. Jacoby, Chemicals from the Garden,C&EN 26-28 (2009). Strong acids are often used; however, the use ofthese requires the refining of the cellulosic materials to ensuresufficient contact between the acid and the biomass. See e.g., U.S. Pat.No. 5,562,777. Such methods further result in large amounts of wasteproducts, incurring additional costs.

Therefore, it is an object of the present invention to develop methodsof converting cellulose and related carbohydrate materials tocommercially-useful low-molecular-weight compounds.

It is a further object of the present invention to develop methods toconvert cellulose and related carbohydrate materials to ethylene glycol,propylene glycol, glycerin, methanol, hydroxyacetone, glycolaldehyde anddihydroxyacetone.

A still further object of the present invention is to develop a singlestep conversion method to produce the low-molecular-weight compoundswithout the need for hydrogen gas, strong acids, metal catalysts, orenzymes.

BRIEF SUMMARY OF THE INVENTION

The invention overcomes the problems associated with prior arttechniques, as well as other problems as will become apparent herein.According to one aspect of the invention, novel methods of convertingbiomass sources, including both agricultural and municipal wastesources, to finished high-value products in a one-step method arepresented. The cellulose and other related carbohydrate materials, suchas glucose and other monosaccharide sources, according to the inventiongenerate high yields of ethylene glycol, propylene glycol, glycerin,methanol, hydroxyacetone, glycolaldehyde and dihydroxyacetone. Inanother aspect of the invention, batch and continuous methods of biomassconversion that do not necessitate the use of catalysts are presented.

According to the invention, a process for cellulose conversion intolow-molecular-weight compounds comprises contacting a cellulose orrelated carbohydrate material source with a low-molecular-weight alcoholto form a reaction mixture in a reactor, employing a co-solvent with thelow-molecular weight alcohol, heating the reaction mixture under hightemperature and pressure conditions for the reaction mixture to undergothermal decomposition, and converting the cellulose or relatedcarbohydrate material source into low-molecular-weight compounds.According to a preferred embodiment of the invention, thelow-molecular-weight alcohol is ethanol, 1-propanol, 1-butanol,2-butanol or 2-propanol. According to additional embodiments of theinvention, the reaction mixture is cooled to enable separation of liquidand solid phases.

According to additional embodiments of the invention, the temperature inthe reactor ranges from about 250° C. to about 375° C. and the pressureranges from about 1000 psi to about 3500 psi. The reaction mixture isheated under high pressure conditions for a period of time between about20 minutes to about 2 hours. Additionally, the cellulose conversionmethods comprise a first conversion step to convert the cellulose orrelated carbohydrate material source to glucose, a mono- or smalloligosaccharide prior to combining with said low-molecular-weightalcohol. According to such embodiment of the invention, the reactionmixture is not sensitive to impurities and does not produce glucoside orlevoglucosan products. According to additional embodiments of theinvention, a reaction mixture is heated to a critical temperature andcritical pressure to create a supercritical fluid.

A process for producing ethylene glycol, propylene glycol, glycerin,methanol, hydroxyacetone, glycolaldehyde and dihydroxyacetone productsfrom a cellulose or related carbohydrate material source according tothe invention comprises contacting a collection of cellulose or relatedcarbohydrate material source with a low-molecular-weight alcohol and aco-solvent to form a reaction mixture in a reactor, heating the reactionmixture under critical temperature and pressure conditions to produceethylene glycol, propylene glycol, glycerin, methanol, hydroxyacetone,glycolaldehyde and dihydroxyacetone products, and separating andcollecting the products. According to this embodiment of the invention,the reaction does not require the use of a catalyst.

According to additional embodiments of the invention, the temperature inthe reactor ranges from about 250° C. to about 375° C. and the pressureranges from about 1000 psi to about 3500 psi. An additional embodimentof the invention comprises first converting the cellulose or relatedcarbohydrate material source to glucose, a mono- or smalloligosaccharide prior to combining with said low-molecular-weightalcohol. According to such embodiment of the invention, the reactionmixture is not sensitive to impurities and does not produce glucoside orlevoglucosan products.

According to the invention, the preferred low-molecular-weight alcoholis ethanol, 1-propanol, 1-butanol, 2-butanol or 2-propanol andtemperature and pressure conditions approach or exceed the supercriticaltemperature and pressure of the low-molecular-weight alcohol.

An additional embodiment of the invention is a continuous process forthe conversion of cellulose or related carbohydrate material source toform ethylene glycol, propylene glycol, glycerin, methanol andhydroxyacetone products. The embodiment for a continuous processcomprises continuously feeding a reactor a source of cellulose or arelated carbohydrate material, combining a low-molecular-weight alcoholto the source of cellulose or a related carbohydrate material to form areaction mixture, maintaining a constant temperature and pressurecondition of the reaction mixture, and separating ethylene glycol,propylene glycol, glycerin, methanol and hydroxyacetone products fromthe reaction mixture. According to this embodiment of the invention, thetemperature and pressure conditions cause thermal decomposition of thereaction mixture and eliminate the need for a catalyst or additionalreagents.

According to this embodiment of the invention, the temperature in thereactor is at least about 250° C. and the pressure ranges from about1000 psi to about 3500 psi. According to an additional embodiment, thereaction mixture is heated to a critical temperature and criticalpressure to create a supercritical fluid. The process may furthercomprise a first conversion step to convert the source of cellulose orrelated carbohydrate material to glucose, a mono- or oligosaccharidebefore feeding into the reactor. The process according to thisembodiment of the invention results in a reaction mixture that is notsensitive to impurities and does not produce glucoside or levoglucosanproducts.

These and other embodiments of the invention will be readily apparentbased on the disclosure of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of a non-limiting embodiment of a batch reactorfor use according to the invention.

FIG. 2 shows a diagram of a non-limiting embodiment of a campaignreactor for use according to the invention.

FIG. 3 shows a diagram of a non-limiting embodiment of a continuousreactor for use according to the invention.

FIGS. 4 and 5 show diagrams of a non-limiting embodiment of theinvention showing residence time distribution (ethylene glycol % vs.time in minutes).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The embodiments of this invention are not limited to particular methodsof biomass conversion, which can vary and are understood by skilledartisans. It is further to be understood that all terminology usedherein is for the purpose of describing particular embodiments only, andis not intended to be limiting in any manner or scope. For example, asused in this specification and the appended claims, the singular forms“a,” “an” and “the” can include plural referents unless the contentclearly indicates otherwise. Further, all units, prefixes, and symbolsmay be denoted in its SI accepted form. Numeric ranges recited withinthe specification are inclusive of the numbers defining the range andinclude each integer within the defined range.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which embodiments of the invention pertain. For example, psishall mean pound per square inch or pound-force per square inch as isunderstood by those of skill in the art.

Many methods and materials similar, modified, or equivalent to thosedescribed herein can be used in the practice of the embodiments of theinvention without undue experimentation, the preferred materials andmethods are described herein. In describing and claiming the embodimentsof the invention, the following terminology will be used in accordancewith the definitions set out below.

The terms “biomass” and “carbohydrate material,” as used herein, refersto any source of cellulosic and/or lignin/lignocellulosic biomass,including for example, wood, municipal waste, trees or parts thereof,forest product residues, energy crops, straw, grass, corn, corn husks,paper and paper products, animal, agricultural and human wastes, sewagesludge, and living or dead plants. Accordingly, biomass includes any ofwood, cellulose, hemicellulose, lignin, lignocellulosic materials, ormixtures thereof, paper, as well as wastes and residues from forests,animals, and humans, including municipal waste, that are at leastpartially organic in their makeup, and any plant material or residue ofa plant, whether such plant or residue is living or not. As used herein“biomass” and “carbohydrate material” may further include sources ofcellulose, glucose and other sources of simple sugars disclosedaccording to the invention.

The term “cellulose,” as used herein, refers to a polysaccharideconsisting of a linear chain of several hundred to over ten thousandβ(1,4) linked D-glucose units. Cellulose as used herein further refersto any source of cellulosic and/or lignocellosic biomass.

The term “catalyzed,” as used herein, refers to the use of any compound,enzyme or other catalyst to increase the rate of a chemical reaction.Biomass conversion often requires the use of enzymatic catalysis, suchthat an enzyme catalyzes the conversion of a substrate into a product.Alternatively, the depolymerization of cellulose has been catalyzed bycombining copper chloride and chromium chloride dissolved in animidazolium ionic liquid. (C&EN, 87(27):26-28 (2009)).

The term “low-molecular-weight alcohol,” as used herein refers tosaturated alcohols having one to ten carbon atoms. Alow-molecular-weight alcohol according to the invention is a reducingalcohol that is capable of bringing about an uncatalyzedMeerwein-Ponndorf-Verley (MPV) reaction. According to various preferredembodiments of the invention, low-molecular-weight alcohol may includeboth primary and secondary alcohols, including for example, ethanol,1-propanol, 1-butanol, 2-butanol and 2-propanol. According to anadditional embodiment, low-molecular-weight alcohol may further includecyclic alcohols, such as cyclohexanol, and diols such as1,5-pentanediol. A preferred embodiment of the invention includessecondary alcohols, such as 2-propanol or isopropyl alcohol, as the lowlow-molecular-weight alcohol for biomass conversion. However, as oneskilled in the art will appreciate, tertiary alcohols, including forexample tert-butyl alcohol, do not function as reducing alcohols for MPVreactions and are not suitable for use as a low-molecular-weight alcoholaccording to the invention.

The term “supercritical alcohol,” as used herein refers to an alcoholthat becomes a supercritical fluid (SCF). For example, according to theinvention, when a low-molecular-weight alcohol, such as 2-propanol, isheated to its critical temperature (T_(c)=235° C.) under its criticalpressure (P_(c)=at least 691 psi of pressure), the gas phase and liquidphase merge to form a supercritical fluid. A supercritical fluid orspecifically a supercritical alcohol, as may be applicable according toembodiments of the invention, results from a gaseous and liquid portionconfined to a limited volume under both elevated temperature andpressure. As such temperature and pressure are increased, gas moleculesare forced closer together and the liquid molecules are forced fartherapart; resulting in the two phases forming a single SCF phase above aprecise critical temperature and critical pressure.

According to embodiments of the invention, an alcohol or fluid maybecome a supercritical alcohol or SCF upon reaching its criticaltemperature (T_(c)) and its critical pressure (P_(c)). However,according to alternative embodiments of the invention, the methods ofthe invention do not necessitate use of a supercritical alcohol or SCF.Temperatures and pressure may be decreased below SCF conditions or maynot reach levels to achieve SCF conditions and still yield the desirableresults according to the methods of the invention. Therefore, themethods of the invention for converting cellulosic biomass intolow-molecular-weight compounds may comprise reacting a collection ofbiomass with an alcohol, wherein the mixture with the alcohol is heatedat high temperatures and under high pressure. According to analternative or optional embodiment of the invention, such methods maycomprise heating the mixture and alcohol to a critical temperature andcritical pressure to create a SCF.

The methods of the invention produce two sets of products directly,without the need or use of any catalyst or additional reagents.According to an embodiment of the invention, the methods do not useacids as a reagent for biomass conversion. Beneficially, the use ofstrong acids is obviated, in addition to the use of catalysts. The useof strong acids is incompatible with the methods of the presentinvention, as a result of the high temperatures which would be expectedto corrode the reactors, namely stainless steel reactors. In thealternative, the methods according to the invention for biomassconversion use alcohols as weak acids under the conditions set forthaccording to the embodiments of the invention. Therefore, it is anembodiment of the invention that high temperature and pressureconditions permit the use of alcohols rather than strong acids,catalysts or other reagents.

Production of Low Molecular Weight Compounds

According to the invention, the use of a low-molecular-weight alcoholunder high pressure and temperature conditions converts cellulose intothe following two sets of products: (I) ethylene glycol (EG), propyleneglycol (PG), glycerin (GLOL), hydroxyacetone (HYAC) and methanol (MEOL);and (II) alkyl glucosides and levoglucosan. The group I products areapproximately 30% weight of the products yielded, whereas the group IIproducts represent approximately 15% weight. The production of group IIproducts has been reported. Minami & Saka, J Wood Sci, 51, 395 (2005);Ishikawa & Saka, Cellulose, 8:189-195 (2001) (reporting the conversionof biomass sources using supercritical methanol or other poor reducingalcohols failing to obtain group I products). Notably, the production ofgroup I products in significant yields resulting from simplifiedchemical conversion methods suitable for industrial scale have not beenobtained from prior biomass conversion methods.

According to embodiments of the invention, group I products may furtherinclude glycolaldehyde (HOCH2—CHO) and dihydroxyacetone (HOCH2—CO—CH2OH)in significant quantities. The additional group I products areprecursors to some of the main group I products and may be producedaccording to embodiments of the invention in significant yields.According to the invention, such group I products are obtained as aresult of first reducing biomass cellulose sources to glucose (or othermonosaccharides) and using the alcohols according to the claimedmethods. Accordingly, the invention provides high-value compounds,primarily ethylene glycol, propylene glycol, glycerin, hydroxyacetoneand methanol in addition to the glucose derivatives alkyl glucosides,and levoglucosan previously obtained from biomass conversion methods.

According to the invention, the biomass and carbohydrate materialconversion provides high yields of the high-value compounds, includingethylene glycol, propylene glycol, glycerin, methanol andhydroxyacetone. According to one embodiment of the invention, thehighest yields were of ethylene glycol and propylene glycol from thestarting materials of biomass and carbohydrate material. The relativehigh yields of these high-value compounds are notably achieved frominexpensive methods for converting low-cost starting materials, namelycellulose and biomass. The yields achieved according to the methods ofthe invention are at least comparable or better than the methods of theprior art.

Ethylene glycol and propylene glycol are organic compounds that arecommercially important bulk chemicals that may be produced according tothe methods of the invention from a biomass source. They are alsocommercially valuable and sell at higher prices than ethanol products.For example, ethylene glycol (ethane-1,2-diol) is used as antifreeze andin air conditioning units due to its low freezing point and is often amonomer precursor to numerous polymers, including the very importantpolyester polyethylene terephthalate, which is used in clothing, plasticbottles, etc.

Propylene glycol (propane-1,2-diol) is often used to replace ethyleneglycol for applications requiring safer chemical properties, for examplein food products. Propylene glycol also has a wide variety of usages,including for example, pharmaceutical solvents, cosmetic applications,toothpastes, mouth wash, a monomer precursor to polymers, including thewidely used unsaturated polyester resins, brake and hydraulic fluids,paints and coatings, laundry detergents, pet food, tobacco, shampoos,deodorants, food coloring and flavorings, and less-toxic antifreeze.

Glycerin is an organic compound commonly known as glycerol(1,2,3-propanetriol) and may further be produced according to themethods of the invention from a biomass source. Glycerin is mostcommonly used as a viscous liquid in pharmaceutical compositions andformulations as a result of its high solubility in water,hygroscopicity, low toxicity and sweet-tasting flavor. Glycerin may befurther utilized in food products for preservation and as a bulkchemical and raw material for use in manufacturing mono-glycerides anddi-glycerides and numerous other chemical reactions. Glycerin is used inmany commonly used products, including cough syrups, toothpaste, shavingcream, soaps, lubricants, and countless other consumer products.

Methanol and hydroxyacetone are also valuable low-molecular-weightproducts. For example, hydroxyacetone can be readily reduced (utilizinghydrogen and a catalyst) to propylene glycol. Accordingly, theproduction of glycerin, methanol and hydroxyacetone from a biorenewablesource at high yields, according to the methods of the invention,provides numerous benefits to be realized by a skilled artisan.

Additionally, glucose derivatives, including alkyl glucosides andlevoglucosan may also be produced according to the methods of theinvention when a cellulose, a cellulosic material (such as paper), alignocellulose material (such as wood), or starch source is utilized.However, according to the invention, once a cellulose or lignocellulosicmaterial is converted to glucose or other monosaccharides beforeundergoing the reactions of the methods of the invention, the thermaldecomposition of monosaccharides produces primarily ethylene glycol,propylene glycol, glycerin, methanol, and hydroxyacetone, rather thanthe glycosides and levoglucosan.

According to the methods of the invention, the ethylene glycol,propylene glycol, glycerin, methanol, and hydroxyacetone products aremore readily and preferably purified than the glucosides, glycosidesand/or levoglucosan. According to a preferred embodiment of theinvention, use of glucose as a starting material for the methods of thisinvention result in production of group I products representingapproximately 60% weight (rather than estimated 30% weight from theconversion of cellulose).

The use of glucose as a starting material to generate increased yieldsof the preferred low-molecular-weight compounds ethylene glycol,propylene glycol, glycerin, methanol, and hydroxyacetone can be extendedto other monosaccharides and/or small oligosaccharides. Glucose is analdohexose, six-carbon monosaccharide aldehyde. The same resultsfavoring the increased production of ethylene glycol, propylene glycol,glycerin, methanol, and hydroxyacetone result from the use of fructose(a ketohexose, six-carbon monosaccharide ketone), xylose (analdopentose, five-carbon monosaccharide aldehyde), sucrose (anon-reducing disaccharide), and other hexoses, pentoses, oroligosaccharides, either aldo-, keto-, or non-reducing.

According to the invention, reference to glucose as a starting material(or treating a cellulose or related carbohydrate material to formglucose) shall be understood to incorporate the use of othermonosaccharides or small oligosaccharides in addition to glucose. Theuse of xylan (hemicellulose) produces slightly lower yields of the groupI products than those obtained from glucose and the xylan does notproduce any levoglucosan as a result of its pentose polymer structure.

According to an alternative embodiment of the invention, the glucosefrom the glucosides could be further utilized to prepare additionalethylene glycol, propylene glycol, glycerin products or purified for avariety of other uses, for example animal foods, cosmetics, etc. as oneof ordinary skill in the art would be capable of achieving based uponthe invention described herein and is considered within the scope of theinvention.

Methods of Cellulose and Related Carbohydrate Material Conversion

According to an embodiment of the invention, methods for convertingcellulose or related carbohydrate material sources into high-value,low-molecular-weight compounds may be obtained from a variety ofcellulose sources. According to one embodiment of the invention, thecellulose source for conversion may include any biomass source orcarbohydrate material. Various exemplary biomass and carbohydratematerials were tested according to the methods of the invention (seeTable 1-3).

Selected biomass sources used according to the methods of the inventionmay first require pretreatment. Pretreatments are necessitated forconversion of cellulose or related carbohydrate materials (such asvarious forms of biomass), as cellulose is a solid and difficult to pumpthrough the systems for the conversion into the low-molecular-weightcompounds according to the invention. Such pretreatments are necessaryfor hydrolysis to occur in order to hydrolyze the applicable startingmaterial to glucose or other sugars. Further description ofpretreatments is disclosed in U.S. Pat. Nos. 5,562,777 and 7,501,025,the disclosure of which are herein incorporated by reference in itsentirety.

According to another embodiment of the invention, a pretreatment mayalternatively convert a starting material into a monosaccharide,disaccharide, trisaccharide, or chains of saccharides, producing a watersoluble starting material for the methods of the invention describedherein. According to the invention, the pretreatment of a lignocellulosewould yield glucose, pentose and lignin, requiring the preferred removalof lignin prior to following the methods of the invention.

Pretreatment methods, as known by those skilled in the art, may includeswelling of the biomass by adding a liquid source to the biomass, forexample by addition of water for hydrolysis to occur and to create awater soluble starting product for the methods of the invention.Alternatively, biomass utilized in the methods of the invention may bemilled in dry conditions to separate bran from the biomass. Any methodsknown in the art can be used for the separation of the bran, forexample, the bran may be separated by sieves. One skilled in the artwill recognize that the particular form of biomass or cellulose selectedfor use according to the conversion methods of the invention, mayrequire additional handling and conversion considerations. For example,the conversion of paper waste is distinct from agricultural or municipalwaste.

Modifications of a pretreatment method in order to adapt to a particularbiomass starting material are intended to fall within the scope of theinvention as it will be apparent to those skilled in the art the variouschanges and modifications of the embodiments of the invention to adaptit to various usages and conditions. The use of a pretreatment tohydrolyze the cellulose or biomass to glucose is expected to result inimpurities. Beneficially as discovered by the inventors, according tothe invention, the methods set forth below are not sensitive to suchimpurities. Accordingly, glucose sources resulting from a pretreatedcellulose or biomass are efficiently converted to the ethylene glycol,propylene glycol, glycerin, methanol and hydroxyacetone products withvery small quantities, if any, of glucosides and levoglucosan produced.

Biomass utilized according to the methods of the invention, may requiresize reduction in addition to a pretreatment. If necessary, any processfor reducing the size of biomass may be utilized either before or afterany pre-treatment of the biomass, as known according to those skilled inthe art; for example, biomass may be reduced by milling to granule sizesas small as less than 1 mm, or preferably to smaller sizes less than 0.8mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, or 0.2 mm. The selection of thepreferred particle size of a biomass source may be selected andperformed by methods known in the art, including for example by sieves.

According to an embodiment of the invention, biomass is converted tosuch high-value compounds by thermal decomposition in high boilingsolvents wherein the cellulose and lignocellulose of the biomass areheated under high temperature and high pressure conditions. According toanother embodiment of the invention, the mixture may include asupercritical alcohol or SCF. According to a particular embodiment, themixture of a particular carbohydrate material and a low-molecular-weightalcohol are placed in a stainless steel reactor.

According to another embodiment of the invention, the cellulosicmaterial may first be pretreated to enable its break down into glucoseor other mono- or small oligosaccharides. Such pretreatment enables theproduction of the preferred products of ethylene glycol, propyleneglycol, glycerin, methanol, and hydroxyacetone rather than theglucosides and levoglucosan, as a result of the initial conversion ofthe cellulose or carbohydrate material into preferably glucose or othermono- or small oligosaccharides. Therefore, according to a preferredembodiment of the invention, a cellulose or biomass source is firstconverted to glucose or other mono- or small oligosaccharides prior toundergoing thermal decomposition using high boiling solvents and highpressure conditions.

According to an embodiment of the invention, a low-molecular-weightalcohol, such as 2-propanol, may further contain additives, such aswater. These and other solvents and/or co-solvents may be employed. Inan aspect, a low-molecular weight alcohol is employed as a co-solvent.In an aspect, water is employed as a co-solvent. In a further aspect,members selected from the group consisting of 2-pentanol, propyleneglycol, isopropyl ether, water, 2-methoxyethanol, sulfolane, ethanol,diisopropyl amine and combinations of the same are employed as solventsand/or co-solvents. The solvents and co-solvents disclosed herein areeffective for solubilizing the biomass cellulose sources and the biomassconversion methods of the present invention.

In an aspect, the use of the solvents and/or co-solvents can be in therange of solvent:co-solvent from about 100:1 to about 1:10, preferablyfrom about 10:1 to about 1:1. The relative amounts of solvent toco-solvent will vary depending upon the biomass source employed for themethods of the invention, and the variation in reaction conditionsaccording to the invention, including without limitation reaction time,residence time, type of reactor, pressure, temperature and the like.

The low-molecular-weight alcohol and cellulose or related carbohydratesource are placed in a reactor according to the methods of theinvention. Once inside the reactor, the mixture is heated and optionallystirred. The mixture is heated to high temperature conditions,preferably ranging from about 250° C. to about 375° C., more preferablyfrom about 275° C. to about 350° C., most preferably from about 300° C.to about 325° C. The amount of alcohol used in the mixture according tothe invention is determined such that the pressure of the system risesto preferably about 1000 psi to about 3500 psi, more preferably about2000 psi to about 3500 psi at the maximum temperature.

According to an embodiment of the invention, the amount of thelow-molecular-weight alcohol used for a reaction may vary. According toa preferred embodiment the low-molecular-weight alcohol is added in avolume sufficient to fill the reactor about half full at roomtemperature. According to an embodiment of the invention,low-molecular-weight alcohols have a density at room temperature abouttwo times that of the supercritical fluid at 300° C.

In one particular embodiment of the invention a mixture of cellulose andisopropyl alcohol are placed in a reactor and heated above thesupercritical temperature (Tc) of the isopropyl alcohol (235° C.) withsufficient quantities of the alcohol to generate pressure above thesupercritical pressure of isopropyl alcohol (691 psi). Beneficially,according to the invention, these methods of biomass conversiondescribed herein and apparent to a skilled artisan do not require theuse of a catalyst and are not sensitive to impurities.

According to the invention, the methods of biomass conversion do notnecessitate the use of any catalysts, providing a significant benefitover biomass conversion methods employed by others requiring catalysts.As a result, according to the invention, the methods of biomassconversion overcome significant burdens faced by those skilled in theart at the time of the invention by eliminating the additional expenseof catalysts, eliminating the requirement of removal and/or recycling ofcatalysts, not producing unwanted byproducts as a result of use ofcatalysts, eliminating effects of impurities caused by catalysts in thebiomass conversion process, etc.

According to one embodiment of the invention, the reaction mixture isheated to elevated temperatures, from a few minutes to several hours.According to embodiments of the invention wherein the methods include aninitial conversion of a cellulose or carbohydrate material into glucoseor other mono- or small oligosaccharides, the length of time for thereaction is preferably between about 5 minutes to about 2 hours, morepreferably between about 20 minutes to about 60 minutes. According toembodiments of the invention wherein the methods do not includepretreatment for the conversion of a biomass or cellulose source, thelength of time for the reaction is preferably between about 1 hour toabout 4 hours, more preferably between about 1 hour to about 2 hours.However, as one skilled in the art shall ascertain based upon thedisclosure of the present invention, modifications of temperature andpressure conditions, among other variables, may further modify theamount of time for the reactions according to the invention. Suchvariations are intended to be within the scope of the claimed invention.

After heating the mixture to elevated temperatures, from a few minutesto several hours, the reactor is cooled to room temperature to obtainthe reaction mixture and the high-value compounds produced by thebiomass conversion. To obtain the high-value compounds the solid andliquid phases are separated.

According to one embodiment of the invention, separation of thehigh-value compounds may occur by distillation to separate out mixturesof the compounds, as the glycols are thermally stable and thereforeeasily separated from the methanol and hydroxyacetone products bydistillation. Pure methanol and hydroxyacetone can be obtained bydistillation. This is also a preferred method to physically separate theglycerin products from the ethylene glycol and propylene glycol productswithout requiring any chemical reaction to separate the products.Further separation of the ethylene glycol from the propylene glycolproducts may also be done according to more careful distillation.

Additional separation methodologies may be utilized by those skilled inthe art. After separation of the high-value compounds, additional stepsmay be necessitated according to the desired use of the compounds, aswill be ascertained by those of ordinary skill in the art, including forexample, purification, refining, extraction or other types of processingof the high-value compounds. For example, purification of the compoundsmay be necessary, such as purification of the propylene glycol if it isto be used in food products.

According to another embodiment of the invention, the cellulose orrelated carbohydrate material conversion into high-value compounds bythermal decomposition in high boiling solvents, optionally such assupercritical alcohols or SCF, may be done in a batch process,campaign-type process or a continuous process.

Batch processing methods according to an embodiment of the inventioninclude placing the mixture from a particular biomass or carbohydratematerial with the low-molecular-weight alcohol into a stainless steelreactor in aliquots. The reactor containing the mixture is heated andstirred to reach a temperature that may range from about 250° C. toabout 375° C. and pressure of from about 1000 psi to about 3500 psi atthe maximum temperature, more preferably from about 275° C. to about355° C., most preferably from about 300° C. to about 325° C. andpressure from about 2000 psi to about 3500 psi at the maximumtemperature. The mixture is heated and stirred for a sufficient periodof time, ranging from a few minutes to several hours in order to obtainthe desired high-value compounds.

According to an embodiment of the invention, the batch processingrequires the reactor be cooled down and the pressure reduced betweenbatches. Once the reactor is cooled, then high-value compounds may beobtained from the reactor. According to one embodiment of the invention,the reactor is operated at about 300° C. and about 2000 psi, which wouldrequire cooling down and lowering the pressure to approximately roomtemperature (about 30° C.) and approximately one atmosphere (about 14.5psi) before running another batch through the reactor. Such a processmay take hours for a large reactor or alternatively may takeapproximately an hour for a small reactor to cool to these temperatureconditions and decrease the pressure.

Alternatively, a series of smaller batches or campaign-type process maybe utilized under the methods of the invention to provide for enhancedmethods of increased production of the ethylene glycol, propyleneglycol, glycerin, methanol, and hydroxyacetone. According to anembodiment of the invention, a campaign-type process involves thesolvent and starting materials (such as glucose, cellulose, or a biomasssource) being pumped into a reactor. The reactor is heated and thereaction is run under high pressure. After allowing time for thereaction to take place, the reaction mixture is drained from the reactorwith cooling and pressure reduction. After the reaction mixture isremoved from the reactor, the reactor is recharged with solvent andstarting material and the process continues without the need to cool thereactor before a subsequent campaign reaction is initiated.

According to certain embodiments of the invention, particularly suitableconditions for campaign-type processes include the use of an initiallycool reactor, adding a low-molecular weight alcohol (such as2-propanol), heating the reactor to about 275° C. to about 325° C.,pumping in the starting material to run the reaction mixture under highpressure from about 1000 psi to about 3500 psi, draining the productsand cooling the products at the end of the reaction time. Subsequentbatches may be run according to the same methods while using the hightemperature reactor, without the need to cool the reactor and re-heatthe reactor for each subsequent batch. According to the embodiments ofthe invention, campaign-type process generated the same group I productsachieved from both batch and continuous processes and obtained similaryields of the products.

An additional embodiment of the invention is a continuous process formethods of biomass conversion according to the invention to obtainethylene glycol, propylene glycol, glycerin, methanol, andhydroxyacetone. According to an embodiment of the invention, acontinuous process involves the starting material (such as glucose,cellulose or a biomass source) and low-molecular weight alcohol mixturebeing passed through a heated chamber allowing the mixture to reach thehigh temperature and high pressure needed according to the invention.The reaction mixture is pumped under high pressure continuously througha chamber that is under high temperature conditions. The continuouspumping of the reaction mixture through the heated and pressurizedchamber lasts for a sufficient amount of time to allow the reaction toreach completion. Thereafter, the reaction mixture flows out of thechamber with cooling and pressure reduction. The reaction mixture isthen collected and the products are separated.

According to a preferred embodiment of the invention, a reaction mixtureof glucose and 2-propanol is continuously pumped through a chamber thatis heated to a temperature from about 275° C. to about 325° C. and underhigh pressure from about 1000 psi to about 3500 psi. The reactionmixture remains under the high pressure and high temperature conditionsin the chamber for a few minutes to several hours, to ensure thereaction to form the group I products is completed. Then the reactionmixture with the group I products flows out of the chamber for coolingand pressure reduction to separate and obtain the group I products.

According to either of the embodiments of a campaign-type process and/ora continuous process, the need to stop and cool the reactor and bring itto normal pressure conditions as described for a batch process iseliminated. Beneficially, the high-value group I compounds are moreefficiently generated without stopping to cool the temperature and/orreduce the pressure. Therefore, a series of smaller batches or thecontinuous process is advantageous in that it does not require theinactivation of the reactor to open and remove the high-value compoundsproduced by the methods of the invention. Rather, either provides ameans for continuously removing generated product from the reactor.

Benefits of utilizing a campaign-type process or a continuous processinclude increased product yield, including yield consistency andquality, reduction of manufacturing costs and reduction of wasteproducts, all providing an efficient and cost-effective commercialprocess for making the high-value compounds according to the invention.Additionally, use of a campaign-type process or a continuous processyields safer methods, in addition to more efficient methods, as a resultof the ability to process relatively smaller amounts at a continuouspace. Therefore, the use of larger batches to generate industrialamounts of the high-value compounds with the batch process isefficiently replaced with either a series of smaller batches or thecontinuous process.

Those of skill in the art may implement modifications and changes toeffectuate the continuous process described herein according to themethods of the invention. This and other optimization of a process iswithin the skill of the artisan and is incorporated within the scope ofthe invention.

EXAMPLES

Embodiments of the invention are further defined in the followingnon-limiting Examples. It should be understood that these Examples,while indicating certain embodiments of the invention, are given by wayof illustration only. From the above discussion and these Examples, oneskilled in the art can ascertain the essential characteristics of thisinvention, and without departing from the spirit and scope thereof, canmake various changes and modifications of the embodiments of theinvention to adapt it to various usages and conditions. Thus, variousmodifications of the embodiments of the invention, in addition to thoseshown and described herein, will be apparent to those skilled in the artfrom the foregoing description. Such modifications are also intended tofall within the scope of the appended claims.

The disclosure of each reference set forth herein this patentapplication is incorporated herein by reference in its entirety.

Example 1

Reaction of cellulose and 2-propanol: A magnetic stirring bar, a 3 gquantity of cellulose, and 150 mL of a mixture of 5% water in 2-propanolwere placed in a 300 mL stainless steel reactor (fitted with a pressuregauge and rated to hold pressures up to 4200 psi). The reactor top wasbolted on, and the reaction chamber was flushed with argon and thenclosed. The reaction vessel is then heated. The vessel and contentsshould be heated to temperatures from 275° C. to 375° C. for a period oftime from 30 minutes to several hours. The vessel is also exposed tohigh pressure conditions, such that the pressure of the reaction chamberreaches from 1500 to 3500 psi. According to a preferred method, thevessel is heated to 325° C. and held at that temperature for at least 1hour to bring the pressure of the 325° C. chamber to approximately 2000psi.

The reaction vessel is then allowed to cool to room temperature, and gassamples are collected from the reaction vessel. The top of the reactoris removed, and the reaction mixture is transferred to a centrifuge tubeand centrifuged to separate the liquid and solid phases of the mixture,and amounts (5 mg dry weight) of sediment are obtained. The reactionsolution is then analyzed by NMR. The solvent and volatile products areremoved on a rotary evaporator, and according to an exemplary reactionof cellulose and 2-propanol, approximately 2.7 g of a thick oil isobtained (containing a small amount of 2-propanol). This material isanalyzed by NMR.

For quantitative NMR analysis, sodium benzoate is used as the standard.The yields of ethylene glycol, propylene glycol, glycerol, isopropylglucosides, and levoglucosan are determined in the thick oil. The yieldsof methanol and hydroxyacetone and acetone are determined in the initialreaction solution. The combined weights of the products derived fromcellulose according to an exemplary run of the methods of the inventionare approximately 1.5 g. The gases, CO and CO2, are analyzed by gaschromatography.

The following equation summarizes this reaction:

The ethylene glycol and propylene glycol are hypothesized to result fromretro-aldol reactions that produce reactive aldehydes from fragmentedglucose (these reactions have been observed for glucose in supercriticalwater; Sasaki, M. et al., Green Chemistry 2002, 4, 285-287). Thealdehydes are rapidly reduced due to the interception of the aldehydesby the 2-propanol or ethanol in a non-catalyzed Meerwein-Ponndorf-Verley(MPV) reduction reaction (there are a few reports of these reactionsusing supercritical 2-propanol, e.g., Sominsky et al., JOC, 2004, 69,1492). The reduction of the aldehydes in the MPV reaction results inglycols, a significantly more stable product than the aldehydes. Thisreaction is temperature dependent, preferring temperatures above 275° C.The MPV reaction normally requires a catalyst to reduce thecarbon-oxygen double bond of a hydroxy group; however, according to thebenefits of the invention no catalyst is required. The production ofacetone in the reactions, as expected for an MPV reaction, is consistentwith this process when 2-propanol is the solvent; acetaldehyde isproduced when ethanol is the solvent. The hydroxyacetone is hypothesizedto be an intermediate in the conversion of dihydroxyacetone to propyleneglycol.

The reactions described herein may be further illustrated according tothe following chemical reactions:

Example 2

For several runs, the recovery of the carbon from the carbohydratematerial was greater than approximately 80%. The various materialsutilized include the following:

Materials Material Source Cellulose, Avicel-PH200 FMC CorporationCellulose, 20 micron Sigma-Aldrich Xylan (oat spelt) Sigma-Aldrich2-propanol, HPLC grade Fisher-Scientific D-glucose, ACS gradeFisher-Scientific Starch Fisher-Scientific Xylose Fisher ScientificFilter paper, ground Whatman Inc. Fructose (99%) commercial sample Oakflour local (BECON) Dried Distiller's Grain and Solubles (DDGS) local(BECON) Corn Stover local (BECON) Ethanol AAPER MethanolFisher-Scientific Sucrose Fisher-Scientific

Various low-molecular-weight alcohols, in addition to 2-propanol, wereutilized in this procedure to convert cellulosic materials tolow-molecular-weight compounds, including for example ethylene glycoland propylene glycol. Such low-molecular-weight alcohols include, butare not limited to, 1-propanol, 1-butanol, 2-butanol and ethanol.

A summary of various yields of products according to the methods of theinvention generated from cellulose and other carbohydrates materials ispresented in Table 1. The amounts of starting material ranged from about1 to 6 grams. The temperatures ranged from 300° C. to 375° C.; pressure,if determined, ranged from 2000 psi to 3500 psi; and the time ofreactions spanned one to several hours.

TABLE 1 Reactions of 2-Propanol with Cellulose and RelatedCarbohydrates^(a) Cellulose Cellulose Cellulose Cellulose Filter CornOak Products:^(b) Avicel Avicel Aldrich Aldrich paper stover flourethylene glycol 0.175 0.192 0.160 0.155 0.148 0.023 0.037 propylene0.077 0.072 0.064 0.066 0.072 0.028 0.031 glycol glycerol ^(c) ^(c) ^(c)^(c) ^(c) ^(c) ^(c) isopropyl 0.053 0.088 0.087 0.073 0.048 0.003 0.025glucoside levoglucosan 0.071 0.090 0.078 0.075 0.025 0.003 0.006hydroxyacetone 0.001 0.013 0.013 0.016 0.032 0.007 0.009 methanol 0.0340.035 0.026 0.015 0.017 0.010 0.011 carbon 0.008 0.006 0.012 0.015 0.0270.026 0.028 monoxide carbon dioxide 0.009 0.008 0.011 0.014 0.024 0.0460.029 Sediment^(d) 0.001 0.002 0.005 0.002 0.022 0.217 0.061Unidentified 0.299 0.301 0.310 0.285 0.319 0.390 0.484 products^(e)Total products^(f) 0.412 0.491 0.428 0.430 0.341 0.074 0.119 acetone^(g)0.549 0.428 0.407 0.117 0.360 0.136 0.202 Xylan Products:^(b) (oat) DDGSStarch Glucose Glucose Xylose Fructose ethylene glycol 0.007 0.018 0.0760.289 0.255 0.259 0.141 propylene 0.016 0.050 0.053 0.149 0.112 0.1310.134 glycol glycerol ^(c) ^(c) ^(c) 0.064 0.080 0.085 0.105 isopropyl0.011 0.000 0.065 ^(c) ^(c) ^(c) ^(c) glucoside levoglucosan 0.000 0.0010.104 ^(c) ^(c) ^(c) ^(c) hydroxyacetone 0.036 0.008 0.013 0.012 0.0520.079 ^(h) methanol 0.002 0.002 0.010 0.065 0.070 0.077 ^(h) carbon0.032 0.014 0.004 0.010 ^(h) ^(h) ^(h) monoxide carbon dioxide 0.0490.047 0.005 0.011 ^(h) ^(h) ^(h) Sediment^(d) 0.133 0.087 0.102 0.001^(h) ^(h) ^(h) Unidentified 0.321 0.483 0.030 0.155 0.243 0.220 0.193products^(e) Total products^(f) 0.071 0.079 0.331 0.600 0.570 0.6310.380 acetone^(g) 0.091 0.084 0.313 0.646 0.640 0.615 ^(h) ^(a)allreactions in 2-propanol or 2-propanol/water ^(b)all yields given ingrams per gram starting material ^(c)amount is too small to determine byNMR ^(d)unidentified products not soluble in alcohol ^(e)unidentifiedproducts soluble in alcohol ^(f)Total identified products derived fromcarbohydrate material. For several runs, the recovery of the carbon fromthe carbohydrate material was determined to be >80%. ^(g)produced by theoxidation of 2-propanol ^(h)not determined

Example 3

Various batch reactions using the Materials of Example 2 were completed.Table 2 presents the yields of products according to the methods of theinvention generated from several simple sugars. In these runs aqueoussolutions of the sugar at room temperature were pumped into the hotalcohol under pressure.

TABLE 2 Reaction of 2-Propanol/Water with Sugars^(a) Products:^(b)Glucose Glucose Fructose Sucrose ethylene glycol 0.268 0.329 0.209 0.225propylene glycol 0.062 0.071 0.082 0.051 glycerol 0.063 0.076 0.0830.071 isopropyl glycolate^(c) 0.036 0.038 0.029 0.026 isopropylacetate^(d) — — — 0.019 hydroxyacetone 0.086 0.092 0.116 0.066 methanol0.064 0.080 0.121 0.063 Sediment^(e) 0.001 0.001 0.000 0.002Unidentified products^(f) 0.146 0.152 0.146 0.262 Total products^(g)0.579 0.685 0.638 0.521 Acetone^(h) 0.518 0.619 0.621 0.529 ^(a)allreactions in 2-propanol/5% water ^(b)all yields given in grams per gramstarting material ^(c)isopropyl ester tentatively assigned as isopropylglycolate ^(d)isopropyl ester tentatively assigned as isopropyl acetate^(e)unidentified products not soluble in alcohol ^(f)unidentifiedproducts soluble in alcohol ^(g)total identified products derived fromcarbohydrate material ^(h)produced by the oxidation of 2-propanol

Example 4

Continuous reactions using the Materials of Example 2 were completed.The yields of products obtained from a continuous run are presented inTable 3. A reaction mixture under high pressure (from approximately 1500psi to 3500 psi) was pumped sequentially through a high temperature zone(from approximately 200° C. to 325° C.), a heat exchanger, abackpressure regulator, and then into a collection vessel. The reactionmixture was generated by pumping an aqueous solution of glucose at roomtemperature into a heated source of 2-propanol (temperature fromapproximately 275° C. to 325° C.) which was being pumped into the hightemperature zone.

TABLE 3 Reaction of 2-Propanol/Water with Glucose in a ContinuousReactor^(a) Products:^(b) Amount ethylene glycol 0.087 propylene glycol0.000 glycerol 0.000 glycolaldehyde^(c) 0.098 isopropyl glycolate^(d)0.025 isopropyl acetate^(e) 0.014 hydroxyacetone 0.107 dihydroxyacetone0.050 methanol 0.023 sediment^(f) 0.000 unidentified products^(g) 0.299identified products:^(h) 0.405 acetone^(i) 0.199 ^(a)Continuous reactionpumped through a stainless steel tube having about a 5 min residencetime and a length to diameter ratio of about 20. Temperature was 300°C., and the sample was collected over a period of 18 min. Glucose inputduring this time was 0.64 g and solvent included 32 mL of 2-propanol/5%water. ^(b)all yields given in grams per gram starting material^(c)Detected by NMR in the D₂O solution as the hydrate but reported asthe aldehyde. ^(d)isopropyl ester tentatively assigned as isopropylglycolate ^(e)isopropyl ester tentatively assigned as isopropyl acetate^(f)unidentified products not soluble in alcohol ^(g)unidentifiedproducts soluble in alcohol ^(h)total identified products derived fromcarbohydrate material ^(i)produced by the oxidation of 2-propanol

The continuous reaction of Example 4 produced significant amounts ofglycolaldehyde, hydroxyacetone, and dihydroxyacetone in addition to theproduction of ethylene glycol, propylene glycol, and glycerol. Althoughnot intending to be limited to a particular theory, it is apparent thatthe mild conditions resulted in the production of lesser quantities ofthe ethylene glycol, propylene glycol, and glycerol. The continuousreaction generates greater yields of the group I products, namelyethylene glycol, propylene glycol, and glycerol under higher temperatureconditions and/or slower flow rates.

Example 5

Various embodiments of reactors may be used according to the invention,including batch, campaign and continuous systems. Non-limiting examplesof such systems are shown, respectively, in FIGS. 1-3.

Regardless of the reactor system 10 utilized for the methods accordingto the invention, the following reaction steps occur: (1) cellulose orbiomass is reacted in supercritical alcohol (or low-molecular-weightalcohol) to break down to smaller saccharide fragments and produceretro-aldol products (glycolaldehyde, glyceraldehyde, formaldehyde),wherein the retro-aldol products can be converted to dihydroxyacetoneand possibly pyruvaldehyde by isomerization and dehydration reactions,including the subset of reactions of retro-aldol reactions of sugars;(2) retro-aldol products react with the solvent by MPV reaction to giveglycols and glycerol plus methanol from formaldehyde. According to theembodiments of the invention, the methods of producinglow-molecular-weight compounds from biomass or other cellulose materialscombine the retro-aldol reactions followed by uncatalyzed MPV reactionsto produce high yields of ethylene glycol and related group I products.The production of ethylene glycol and related group I products does notrequire hydrogenolysis using hydrogen and/or a catalyst to formpropylene glycol and ethylene glycol.

According to an embodiment of the invention, a reactor system 10suitable for batch reactions may comprise, consist of or consistessentially of a reactor 17 housing a heater 16 and agitator 15. A feedpump 20 is in fluid connection with the reactor 17 and provides a feedsource 22 to the system. An outlet valve 19 is connected to the reactor17 contained within the heater 16 in order to remove thelow-molecular-weight products produced according to the methods of theinvention. Optionally, a rupture disc 18 may be included in the system.

According to a further embodiment of the invention, a reactor system 10suitable for campaign reactions may comprise, consist of or consistessentially of a reactor 17 housing a heater 16 and agitator 15. Anoutlet valve 19 is connected to the reactor 17 contained within theheater 16 in order to remove the low-molecular-weight products producedaccording to the methods of the invention. A feed pump 20 is in fluidconnection with the reactor 17 and provides a feed source 22 to provideraw materials to the system. Optionally, a rupture disc 18 may beincluded in the system. In addition, according to an embodiment of theinvention using a campaign reaction, a heat exchanger 24 is inconnection with the outlet valve 19 and has means for coolant exit 26and coolant entrance 28 to the system.

According to an additional embodiment of the invention, a reactor system10 suitable for continuous reactions may comprise, consist of or consistessentially of a reactor 17 housing a heater 16 and agitator 15. A feedpump 20 is in fluid connection with the reactor 17 and provides a feedsource 22 to the system. In addition, a solvent pump 14 is in fluidconnection with the reactor 17 and provides a solvent source 12 to thesystem.

In addition, according to an embodiment of the invention using acontinuous reaction, a heat exchanger 24 is in connection with theheater 16 and has means for coolant exit 26 and coolant entrance 28 tothe system. Optionally, a rupture disc 18 and a backpressure regulator30 may be included in the system, wherein a backpressure regulator 30may be in connection with an outlet 32 for the low-molecular-weightproducts produced according to the methods of the invention.

Variations and derivations to the reaction systems according to theinvention may be made within the scope of the invention. For examplevarious materials may be used for the reactor systems, various optionsfor a heater, such as using a heated ceramic jacket or a liquid medium,etc. Suitable materials include corrosion-resistant materials, such asstainless steel. One skilled in the art will ascertain variousmodifications that can be made to the shape, size and formation of thereaction systems according to the invention, including for examplemodifications to the means used for agitation and heating and/or lengthand shape of components of the reactor systems. The exemplary systemsshown in FIGS. 1-3 are non-limiting examples of the systems according tothe invention.

Example 6

Additional experimentation was carried out in short and long reactorsaccording to embodiments of the invention to determine whether a broadresidence time distribution impacts the product mixtures obtainedaccording to the methods of the invention.

Short Reactors. An experiment was carried out in a short continuousreactor designed to measure the residence time distribution. Publishedsupercritical fluid (SCF) research has used long, thin coils for reactorchambers as well as straight tubes. In an aspect of the invention,shorter, straight tubes were employed for the methods of the invention.The residence time experiments used a fixed amount of EG added to astream of 2-propanol which was being pumped through the continuousreactor. EG is unreactive under these conditions. The experimentinvolved using our short continuous reactor procedure at 300° C., withall of the material fed from the solvent pump at 2.0 mL/min. At timezero, the inlet for the solvent pump was switched from pure 2-propanolto a mixture of 5 wt % EG in 2-propanol. After 30 seconds, the inlet wasswitched back to pure 2-propanol. Note that in addition to the 20-mLbasic reactor volume [0.45 inch ID, length/diameter (L/D)=18], thematerial has to travel through several inches of 0.1 inch ID tubing,most of which is outside the heated reactor zone. The approximate timethe EG solute is delayed by the dead volume of non-reactor tubing is 1-2minutes. Due to the decrease in density of the 2-propanol when heated to300° C., the actual time for the material to flow through the reactor isfive minutes.

Samples were taken from the outlet of the reactor at several intervalsand the EG concentrations were measured by NMR. The chart of residencetime distribution for EG fed to the reactor is shown in FIG. 4 as thesolid line. An exponential fit of the later data points is shown with +marks. The exponential appearance of the data after 8 minutes is anindication the reactor is well mixed after this point, and is behavingmore like a continuous stirred tank reactor.

The results indicate the distribution is somewhat broad. About 10% ofthe material fed into the reactor spends less than ½ of the nominalresidence time (based on plug flow) in the reactor, and about 20% spendsmore than double the nominal residence time in the reactor. It is likelyour product yields were different than would be seen in a reactor withplug-flow conditions.

Long Reactors. The long continuous reactor (38 in. long, 0.20 in. ID)was built with the expectation that it would give better “plug flow”characteristics than the short reactor (8 in. long, 0.44 in. ID). Thesame methods employed for the measurement of residence-time distributionfor the short reactor were again employed for use of the long reactor.

A 30-second long “plug” of 5% EG in 2-propanol was fed into the streamof 2-propanol which was being pumped through the reactor at 2.0 mL/minat 300° C. (at time zero, the inlet for the solvent pump was switchedfrom pure 2-propanol to a solution of 5% EG in 2-propanol). Samples weretaken at the outlet of the reactor at intervals and the EG content wasmeasured by NMR. The EG concentration versus time plot (FIG. 5)represents the residence-time distribution for the reactor system.

The plot for the long reactor shows a relatively symmetricaldistribution with a peak centered at 10 minutes. The distribution forthe short reactor has its peak centered at 6.2 minutes, but theconcentration of EG falls slowly and actually goes above the valves forthe long reactor in the 19- to 23-minute time frame. FIG. 5 shows someimprovement (narrowing) in the residence-time distribution in the longreactor. The change is not a simple narrowing but more a formation of asymmetric peak in the long reactor, compared to the short reactor whichshows the concentration increasing quickly, then dropping slowly in anearly exponential decay. Exponential decay is a characteristic of awell-mixed reactor rather than plug flow.

Plugatyr et al. (J. of Supercritical Fluids 2011, 55, 1014-1018) used asimilar measurement method to ours and reported that relatively narrowdistributions could be obtained with a reactor with length/diameter(L/D) ratio of 100 or more. The long reactor employed in theseexperiments was designed to have an L/D ratio of 200, compared to an L/Dof 18 for the short reactor. Based on the narrower and more symmetricaldistribution from the our longer reactor, it is closer to plug-flowbehavior, but the differences of the residence-time distributions of thetwo reactors are minor.

Part of the broadening of the distribution in both the short and longreactor systems described herein is due to the flow paths outside thereactor, including the feed lines, heat exchangers and backpressurevalve. The volumes of these components were kept as similar as possible(about 8 mL), but geometry had to be slightly different for the longreactor. For instance, the heat exchanger in the long reactor is partlyin a 3-inch coil while it is straight in the short reactor. Theresidence-time distribution that really matters in our sugar reactionsis for the reactor tube only, not the rest of the system, because thereaction mixture stops changing once it is cooled.

Results. The distribution of products and the total yields variedsomewhat, but were very similar. There seem to be greater amounts ofglycolaldehyde in the short reactor runs, possibly related to lesscomplete reaction due to some of the materials having a significantlyshorter than average residence time in that reactor. In the longreactor, very little material spends less than half of the averageresidence time in the reactor, or more than double the average time. Itwas noted that for a given reactor temperature some of the mixing-teetemperatures for the long reactor were lower than those for the shortreactor. Changing the insulation of the mixing tee increased itsrelative temperature and this seemed to boost the total yield ofproducts.

Example 7

The use of solvents other than 2-propanol where further analyzedaccording to the methods of the invention. As described in this example,propylene glycol was employed. There would be some benefits in savingenergy and costs related to distillation if the amount of solventrelative to sugar could be reduced in our supercritical 2-propanolreactions. One approach would be to allow one of the products of ourreaction, PG, to function as part of the solvent mixture. PG is asecondary alcohol, and as such should be able to function as a reducingagent in the Meerwein-Ponndorf-Verley reaction as a substitute for2-propanol.

Reactions were carried out to test the ability of PG to function as areducing agent and solvent in the high temperature reaction of glucose,and to evaluate its stability and usefulness in the production ofglycols. Measuring the yield of small amounts of PG in the presence ofPG as solvent is difficult, but we were able to measure the yield of EG,HYA, and MeOH in these runs, and use them to evaluate the process.

The first experiment with 1.4 g glucose with PG at 300° C. gave a clearsolution with no apparent sediment. The yield of EG was low, about athird of what we have seen for typical 2-propanol solvent reactions. Tosee if we could increase the yield, we increased the loading of glucoseto 3.5 g, and pumped it into a reactor at 325° C. with 10% waterpresent. These conditions are more severe than typical 300° C. runs, butthe higher temperature could have helped the PG to reduce the products.The yield of EG (0.45 g) was still low, about 60% of a typical2-propanol reaction. In addition, a number of products we normally don'tsee were produced (as identified by proton NMR), including n-propanol(about 0.5 g), an apparent dehydration and reduction product of PG.These experiments show glucose can be reacted to make glycols in PG,however, improvement in reaction yields requires additionaloptimization. The results demonstrate that PG could be used as aco-solvent.

Example 8

The use of solvents other than 2-propanol where further analyzedaccording to the methods of the invention. As described in this example,2-pentanol was employed.

Our current method for producing glycols from carbohydrates is done withstarting material loaded at up to about 5% of the weight of the solvent.Opportunities to look at separation of products from solvent in otherways than just distilling the whole product mixture is available if alower polarity solvent is employed that allows phase separation from theproduct. The solvent 2-pentanol is capable of Meerwein-Ponndorf-Verleyreaction, and we carried out some experiments with it.

The runs with glucose or fructose showed that 2-pentanol was not able todissolve the sugars in the way we were feeding them in, and char on thebottom or sides of the reactor was seen. Similar products were seen asin previous runs, but the yields of products were quite low, about 0.2to 0.3 g per g of starting material, compared to 0.6 g/g of startingmaterial for many reactions in 2-propanol. Also, the 2-pentanol did notdissolve the materials well, and some char was seen on the walls or thebottom of the reactor.

The results indicate that 2-pentanol could be used as part of a solventmixture along with 2-propanol. However, when employed alone as a solventit does not seem to have enough polarity to dissolve the sugars. Theremay be different results for biomass raw materials that contain lignin,or if 2-propanol is used in a mixture with 2-propanol.

Example 9

Additional testing using additives, different reaction times, differentconcentrations of carbohydrates and different carbohydrates wereemployed. The effects of cosolvents and modifiers were evaluated. Inthis series of experiments 2-propanol was the main solvent. Using thestandard procedure described in the Examples, 2-propanol and a cosolventwere added to the reactor, and the reactor was heated to 300° C. andapproximately 2000 psi for 1 hour. The glucose amount was 1.4 g and thesolvent amount was 55 g. The glucose solution in water was pumped intothe reactor. After 1 hour, the reactor was cooled, and the products wereanalyzed by NMR. A summary of the products is listed in Table 4.

TABLE 4 Critical Critical Six main Yield propylene Temperature Pressureof Boiling point Cosolvent or products^(b) glycol + of cosolventcosolvent of cosolvent Run # modifier wt(g) hydroxyacetone^(b) ° C.(atm) ° C. 441 Standard, IPA 0.686 0.163  235^(c) 47.0 82 443 isopropyl0.644 0.152 227 31.0 69 ether 10% 446 water 25% 0.429 0.157 374 218. 100452 isopropyl 0.627 0.188 227 31.0 69 ether 20% 455 diisopropyl 0.3100.135 249 29.8 84 amine 1% 456 2-methoxy- 0.634 0.214 325 52.2 124ethanol 10% 458 2-methoxy- 0.441 0.194 325 52.2 124 ethanol 45% 459sulfolane 10% 0.393 0.116  503^(d) 49.2 285 460 ethanol 45% 0.514 0.145 241^(c) 60.6 78

The six main products (b) were ethylene glycol, propylene glycol,glycerol, isopropyl glycolate, hydroxyacetone, and methanol. Isopropylacetate is seen at low levels of 0.01 to 0.02 g per g of startingmaterial, but it is obscured by solvent in some of the cosolvent runs,so it was left out of the comparisons. Yields are reported in g productper g starting material. The data (c, d) were obtained from Gude et al.,J. Chem. Eng. Data 1995, 40, 1025, and Domanska et al., J. Chem. Eng.Data 1996, 41, 624.

Isopropyl Ether. One cosolvent studied was isopropyl ether (IPE), alsoknown as diisopropyl ether. Having the ether functionality, IPE shouldbe less polar than isopropanol, and also it should not serve as ahydrogen donor in Meerwein-Ponndorf-Verley (MPV) reduction. Experimentswith IPE at the 10% level and 20% level were conducted as shown in Table4. In both cases, compared to the standard run, the distribution ofproducts was similar. In the 20% IPE run, it appears less MPV reductionoccurred, since the proportion of the reduced form (PG) versus the HYAform is less compared to the basic 2-propanol run.

Water. The amount of water cosolvent was adjusted to 25% in Run 446, andthe yield of main products fell to 0.429 g per g SM compared to 0.686 gper g SM in the standard 2-propanol run. The HYA amount was slightlyincreased. The greater amount of water might be expected to be moresevere in causing side reactions relating to acidic character of thesolvent. The standard run has 5% water, and it appears that thedesirable amount of water cosolvent is closer to 5% than 25%.

2-methoxyethanol. 2-methoxyethanol has a primary alcohol functionalgroup and an ether functional group. With 2 oxygens it is expected tohave significant polarity as a solvent, and be a better solvent forglucose than a primary alcohol of the same molecular weight. The secondoxygen is expected to increase the acidity of the OH group. In Run 456,10% of the 2-methoxyethanol was used as cosolvent, and the yield of mainproducts was 0.634 g per g SM, down slightly from the standard run. Theyield of PG and HYA was 31% higher for this run than the standard run. Agreater level of 45% of 2-methoxyethanol was used in Run 458, and theyield of main products was decreased by 33% compared to the standardrun. A 10% level of 2-methoxyethanol provides good yields anddemonstrates efficacy for use in additional cellulose experiments.

Sulfolane. Sulfolane is a cyclic compound with 4 carbons and a sulfur inthe ring, with the sulfur in the sulfone state, with 2 oxygens attached.It is also known as 2,3,4,5-tetrahydrothiophene-1,1-dioxide. Sulfolaneis known to help in dissolving cellulose more than other organicsolvents, providing an advantage when using cellulose as the startingmaterial, in particular when using high-temperature 2-propanol. In Run459, 10% sulfolane was used, and the yield of main products was down 43%compared to the standard run. The amount of PG and HYA was down 30%.However, the use of sulfolane did result in increased conversion rate incellulose reactions compared to reactions without the sulfolane.

Ethanol. Ethanol is somewhat similar to 2-propanol in solvent polarityand hydrogen bonding. As a primary alcohol, it is slower to act as aMeerwein-Ponndorf-Verley reducing agent than 2-propanol. We have triedit in the past by itself for glucose reactions, and it yields roughlyhalf as much products as with 2-propanol solvent. With cellulosesubstrate, it was close in yield in comparison to 2-propanol.

Ethanol was used as cosolvent at a level of 45% in Run 460. The reactionsolution was very light colored, and some fine bubbles were releasedwhen the material was removed from the reactor. The amount of the mainproducts was 0.514, down 25% from the standard run. The amounts of PGand HYA fell 11% compared to the standard run. It is surprising that theratio of PG to HYA was not affected much by using ethanol, since it isnot as good a reducing agent as 2-propanol. Considering the large amountof ethanol added, the yields were fairly good, indicating the utility inusing smaller concentrations of the ethanol, e.g. 25%.

Diisoproyl amine. Diisopropyl amine was tried as a cosolvent or modifierat a low level since it is capable of acting as a base, and havingsignificant effects in that way. Run 455 used diisopropyl amine at a 1%level, and the amount of main products was 0.310 g per g SM, down 55%from the standard run. However, there are large peaks that seem toindicate a diisopropyl amine group added to a product fragment. Sinceamines are known to add easily to aldehydes, this is a reasonablepossibility.

Example 10

Additional testing using alternative amounts of water and sugarcompositions were employed. A solvent mixtures containing 5% sugar and20% water at 325° C. and 375° C. was evaluated. Previous testingobtained good yields in fructose runs with 10% water, but not as goodwith 30% water, so we tested 20% water and 5% sugar in a run at 375° C.The yield decreased from 0.69 to 0.57 g/g SM in going from 10% water to20% water. At 325° C., the yield dropped to 0.43 g/g SM. The yields ofEG, glycolaldehyde, and MeOH significantly decreased in the higher-waterruns but the yields of PG and HYA did not decrease as much.

The 20% water level was not favorable to product yield under theseconditions. The higher sugar level, 5%, may also have caused some of thedrop in yield. The products involving the aldehyde materials (and theirreduction products), glycolaldehyde (including EG) and formaldehyde(including MeOH), decreased the most in the presence of higher waterlevels, and we have seen this in previous runs. The ketone HYA and itsreduction product PG were less affected by water level.

The fact that the total yield was even lower at 325° C. as opposed tothe simplistic assumption that the water might cause more severeconditions and therefore a worse yield at the higher temperature. It hasbeen reported that product yields for glucose reacting in supercriticalwater are better at higher temperatures in combination with shorterreaction times. Sominsky et al., J. Supercritical Fluids, 2009, 49,221-226.

Example 11

Fructose runs at temperatures of 200° C. to 350° C. with 5% sugar and2.5% water were evaluated. A run at 200° C. reactor temperature and 200°C. mixing tee was carried out to see if any sign of reaction was seen attemperatures that could be experienced in the mixing tee or in thetubing near it. No reaction was seen in this run, suggesting no reactionoccurs in the mixing tee, although it may affect the temperatures andreaction rates at the inlet of the reactor.

A run at 350° C. was carried out to see if decreasing the temperaturecompared to 375° C. had a favorable effect. It did not, and the yieldfor this run was 0.59 g/g SM, compared to 0.74 for run at 375° C.Further reducing the reactor temperature to 325° C. decreased the yieldto 0.52 g/g SM. An experiment with a shorter residence time withfructose gave a lower yield of 0.59 g/g SM. A run with the temperatureat 300° C. at the inlet of the reactor and 350° C. at the outlet onlygave a yield of 0.35 g/g SM. These experiments reinforce the idea that375° C. seems to be the most favorable temperature for fructose.

Glucose runs 2.5 minutes at 350° C. with 5 or 10% water were alsoevaluated to determine the best conditions for EG and HYA products. Arun that maximized the yield of EG and HYA would be desirable to get thetwo glycols separately in pure form (this assumes the HYA could bereduced to PG in high yield). Two runs were carried out that wereslightly different than a run that gave quite good yields of these 2products. The starting material for this run was glucose. Two changes inone of the runs were an increase in the mixing-tee temperature from 131to 150° C. the internal reactor thermocouple was removed. This run used2.5% glucose and 5% water at 350° C. with a 2.5 min run time.

Total yield was about the same or slightly improved at 0.72 g/g SMcompared to 0.71 g/g SM for the standard run. The yield of EG wasimproved to 0.33 g/g SM compared to 0.29 g/g SM for the standard run.The EG/glycolaldehyde products were mostly in the EG form, and thePG/HYA products were mostly in the preferred HYA form.

The second run used 10% water, compared to 5% water for the first run.This run gave yields nearly the same as the first run. Sometimes theincrease to 10% water has had a negative effect on yield from sugars,but usually the effect is small when the sugar % is in the 2.5% range.If the use of 10% water is helpful for addition of sugar or recycling ofsolvent, then 10% water may be acceptable. Overall, the conditions ofthese runs gave very desirable yields and balance of products.

What is claimed is:
 1. A process for conversion of cellulose or relatedcarbohydrate materials into low-molecular-weight compounds comprising:contacting a cellulose or related carbohydrate material source with alow-molecular-weight alcohol to form a reaction mixture in a reactor;employing a co-solvent with the low-molecular weight alcohol; heatingsaid reaction mixture under high temperature and pressure conditions forsaid reaction mixture to undergo thermal decomposition; and convertingsaid cellulose or related carbohydrate material source intolow-molecular-weight compounds, wherein the low-molecular-weightcompounds are ethylene glycol, propylene glycol, glycerin,hydroxyacetone, methanol, glycolaldehyde and/or dihydroxyacetone, andwherein said reaction does not use a catalyst.
 2. The process accordingto claim 1, wherein said low-molecular-weight alcohol is ethanol,1-propanol, 1-butanol, 2-butanol or 2-propanol, and wherein theco-solvent is selected from the group consisting of a secondlow-molecular-weight alcohol, propylene glycol, isopropyl ether, water,2-methoxyethanol, sulfolane, diisopropyl amine and combinations of thesame.
 3. The process according to claim 1, wherein said reaction mixtureis cooled to separate a liquid phase and a solid phase.
 4. The processaccording to claim 1, wherein the temperature in said reactor is fromabout 200° C. to about 375° C.
 5. The process according to claim 1,wherein the pressure in said reactor is from about 1000 psi to about3500 psi.
 6. The process according to claim 1, wherein said mixture isheated in said reactor for a period of time between about 20 minutes toabout 2 hours.
 7. The process according to claim 1, further comprisingthe separation and collection of the low-molecular-weight compoundethylene glycol.
 8. The process according to claim 1, further comprisingthe separation and collection of the low-molecular-weight compoundpropylene glycol.
 9. The process according to claim 1, furthercomprising first converting said cellulose or related carbohydratematerial source to glucose, a mono- or small oligosaccharide prior tocombining with said low-molecular-weight alcohol, and wherein saidreaction mixture is not sensitive to impurities and does not produceglucoside or levoglucosan products.
 10. The process according to claim1, further comprising the separation and collection of thelow-molecular-weight compounds glycerin, methanol and hydroxyacetone.11. The process according to claim 1, wherein said reaction mixture isheated to a critical temperature and critical pressure to create asupercritical fluid.
 12. A process for producing ethylene glycol,propylene glycol, glycerin, methanol, hydroxyacetone, glycolaldehyde anddihydroxyacetone products from a cellulose or related carbohydratematerial source comprising: contacting a collection of cellulose orrelated carbohydrate material source with a low-molecular-weight alcoholand a co-solvent to form a reaction mixture in a reactor; heating saidmixture under critical temperature and pressure conditions to producesaid ethylene glycol, propylene glycol, glycerin, methanol,hydroxyacetone, glycolaldehyde and dihydroxyacetone products, whereinsaid reaction does not use a catalyst; and separating and collectingsaid products.
 13. The process according to claim 12, wherein thetemperature in said reactor is from about 200° C. to about 375° C. 14.The process according to claim 12, wherein the pressure in said reactoris from about 1000 psi to about 3500 psi.
 15. The process according toclaim 12, further comprising first converting said cellulose or relatedcarbohydrate material source to glucose, a mono- or smalloligosaccharide before combining with said low-molecular-weight alcohol,and wherein said reaction mixture is not sensitive to impurities anddoes not produce glucoside or levoglucosan products.
 16. The processaccording to claim 12, wherein said low-molecular-weight alcohol isethanol, 1-propanol, 1-butanol, 2-butanol or 2-propanol, wherein theco-solvent is selected from the group consisting of a secondlow-molecular-weight alcohol, propylene glycol, isopropyl ether, water,2-methoxyethanol, sulfolane, diisopropyl amine and combinations of thesame, and wherein said temperature and pressure conditions approach orexceed the supercritical temperature and pressure of saidlow-molecular-weight alcohol.
 17. A continuous process for theconversion of cellulose or related carbohydrate material source to formethylene glycol, propylene glycol, glycerin, methanol and hydroxyacetoneproducts comprising: continuously feeding a reactor a source ofcellulose or a related carbohydrate material; combining alow-molecular-weight alcohol and a co-solvent to said source ofcellulose or a related carbohydrate material to form a reaction mixture;maintaining a constant temperature and pressure condition of saidreaction mixture in said reactor, wherein said temperature and pressureconditions cause thermal decomposition of said reaction mixture and donot employ a catalyst or additional reagents; and separating ethyleneglycol, propylene glycol, glycerin, methanol and hydroxyacetone productsfrom said reaction mixture.
 18. The process according to claim 17,wherein the temperature in said reactor is at about 200° C. to about375° C. and the pressure is from about 1000 psi to about 3500 psi. 19.The process according to claim 17, wherein said reaction mixture isheated to a critical temperature and critical pressure to create asupercritical fluid and further comprising first converting said sourceof cellulose or related carbohydrate material to glucose, a mono- oroligosaccharide before feeding into said reactor.
 20. The processaccording to claim 17, wherein said reaction mixture is not sensitive toimpurities and does not produce glucoside or levoglucosan products, andwherein glycolaldehyde and dihydroxyacetone products are furtherproduced and separated from said reaction mixture.